Decreased sensitivity to vibratory stimuli, impairment of body position sense, and, occasionally, decline in fine tactile discrimination are some of the symptoms commonly associated with disease or trauma of the dorsal columns in man. In recent years animal experiments and scattered clinical observations claimed that damage to this major afferent pathway failed to cause clear-cut sensory deficits, contrary to the functional definitions accepted by most physiologists and neurologists. Recent results from this laboratory revealed that normal cutaneous sensory detection thresholds could be obtained from the hindlimbs of carnivores under conditions in which the anterolateral pathways of the spinal cord were functionally intact. The experimental protocols presented in this proposal show that the monkey will be trained to operate a manipulandum in response to sensory cues mediated by the isolated dorsal columns. Sensory detection thresholds as well as sensory discrimination thresholds for joint angle and 2-point tactile stimuli will be measured in this primate preparation. The experiments are designed to reveal the intrinsic sensory properties of the dorsal column system in isolation and to compare these with sensory properties of the intact monkey.